An antenna is a specialized electronic device that converts energy from one form to another. An antenna couples radio waves in free space to electrical current used by electronic equipment, such as a portable radio, a mobile radio, and the like. In reception, the antenna intercepts some of the power of an electromagnetic wave in order to produce a voltage that a receiver of the coupled electronic equipment can amplify. During transmission, the electronic equipment produces radio frequency (RF) current that may be applied to terminals of the antenna in order to convert it into an electromagnetic wave (radio wave) radiated into free space.
Depending on the design of the antenna, radio waves can be sent toward and received from all horizontal directions (“omnidirectional”), typically with reduced performance in one or more directions, such as the sky or the ground. Alternatively, a directional or beam antenna may be designed to operate in a particular direction. There are notable physical differences in the design of antennas for different frequencies and purposes. Nevertheless, there are certain basic properties that define the function and operation of antennas. One of the properties most often of interest in the design of antennas is the radiation pattern. The radiation pattern of the antenna determines the spatial distribution of the radiated energy. For example, a vertical wire antenna gives uniform coverage in the horizontal (azimuth) plane, with some vertical directionality, and as such is often used for broadcasting purposes. As an alternative to a radiation pattern providing a uniform coverage, an antenna can have a directional radiation pattern.
In the field of wireless communication, there has been a recent trend to provide wireless communication devices that are operable in more than one frequency band. Examples of wireless communication devices include portable radios, mobile radios, mobile telephones, and the like. For example, these wireless communication devices may be designed to operate in 850/1900 Mega Hertz (MHz) bands, used, for example, in the Americas and/or the 900/1800 MHz bands used in other parts of the world. It will be appreciated that the configuration of an antenna suitably operable in a plurality of discrete frequency bands may impact the design of an associated wireless communication device.
In addition, the complexity of communications devices has increased such that communication devices typically serve multiple purposes. For example mobile telephones capable of operating on different frequency bands are likely to have built in satellite location functionality based on the Global Positioning System (GPS). As noted previously, the radiation pattern of omnidirectional antennas is typically reduced in certain directions such as the sky or the ground. Therefore, even though a wireless communication device with an omnidirectional antenna may include a GPS feature, because the vertical directionality of omnidirectional antennas is typically reduced in the direction of the sky or the ground, there remains room for optimization with respect to the GPS feature in wireless communication devices which incorporate omnidirectional antennas. It is well recognized by skilled artisans in the field of antenna design that it is very difficult to design a single antenna structure that is able to provide similar radiation performance in the horizontal plane and in the direction of the sky or the ground.
Accordingly, there is a need for an optimized antenna configuration suitable for a wireless communication device with optimized radiation performance in both the horizontal plane and in the direction of the sky.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.